1. Field
The following description relates to optical technology, and more particularly, to a method of constructing a physical lens based on depth-of-focus characteristics and an axially symmetric lens with an extended depth of focus constructed using the method.
2. Description of the Related Art
A depth of focus (DOF) is a significant characteristic of an optical system which specifies a range of distance between an object plane and a lens, or a range of distance between the lens and an image plane, within which a clean image can be obtained. Aperture size and various aberrations of a lens are critical factors for determining the DOF.
A general optical system using thin lens approximation is not appropriate for use in many industrial fields such as laser material processing, lithography, and light projection and image processing. Therefore, there is increasing need in such industrial fields for an optical system with a higher DOF.
Korean Patent Application No. 2008-43428 filed by the present applicant discloses a lens with a symmetric and continuous surface having a simple point spread function (PSF) that generates a clear image regardless of a distance from an object. The lens of the related art includes a plurality of axially symmetric layers, each of which has an extended depth of focus and focuses light onto a corresponding segment among a plurality of linear segments of focal curves located on an optical axis. The lens is included in an optical system to generate a clear image, along with an image sensor and an image processor for restoring an image sensed by the image sensor.